System and method for locating buried pipes and cables with a man portable locator and a transmitter in a mesh network

ABSTRACT

A system and method for locating buried cables, pipes and other utilities includes a man portable receiver/locator which is linked by a wireless mesh connection to a transmitter which either directly applies, or induces, a signal onto a buried utility.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit, under 35 USC Sections 119(e)(1) and120, of the filing dates of U.S. Provisional Application Ser. No.60/806,708 filed Jul. 6, 2006 and U.S. Provisional Application Ser. No.60/806,837 filed Jul. 10, 2006, both of Mark S. Olsson et al. and bothentitled “Mesh Networked Wireless Buried Pipe and Cable LocatingSystem.”

BACKGROUND OF THE INVENTION

There are many situations where is it desirable to locate buriedutilities such as pipes and cables. For example, prior to starting anynew construction that involves excavation, it is important to locateexisting underground utilities such as underground power lines, gaslines, phone lines, fiber optic cable conduits, CATV cables, sprinklercontrol wiring, water pipes, sewer pipes, etc., collectively andindividually referred to hereinafter as “utilities” or “objects.” Asused herein the term “buried” refers not only to objects below thesurface of the ground, but in addition, to objects located inside walls,between floors in multi-story buildings or cast into concrete slabs,etc. If a back hoe or other excavation equipment hits a high voltageline or a gas line, serious injury and property damage can result.Severing water mains and sewer lines leads to messy cleanups. Thedestruction of power and data cables can seriously disrupt the comfortand convenience of residents and cost businesses huge financial losses.

Buried objects can be located by sensing an electromagnetic signalemitted by the same. Some cables such as power lines are alreadyenergized and emit their own long cylindrical electromagnetic field.Location of other conductive lines necessitates their energizing with anoutside electrical source having a frequency typically in a range ofapproximately 50 Hz to 500 kHz. Location of buried long conductors isoften referred to as “line tracing.”

A sonde (also called a transmitter, beacon or duct probe) typicallyincludes a coil of wire wrapped around a ferromagnetic core. The coil isenergized with a standard electrical source at a desired frequency,typically in a range of approximately 50 Hz to 500 kHz. The sonde can beattached to a push cable or line or it may be self-contained so that itcan be flushed. A sonde generates a more complex electromagnetic fieldthan that produced by an energized line. However, a sonde can belocalized to a single point. A typical low frequency sonde does notstrongly couple to other objects and thereby produce complex interferingfields that can occur during the tracing. The term “buried objects” asused herein also includes sondes and buried locatable markers such asmarker balls.

Besides locating buried objects before excavation, it is furtherdesirable to determine the depth of the objects. This is generally doneby measuring the difference in field strength at two locations. Althoughvarious methods of determining depth of buried conductors arewell-established, it is also well known that prior methods can producevariable results and potentially dangerous errors in depth estimationwhen in the presence of complex or distorted fields. The presentinvention ameliorates this situation by taking advantage of improvementsin network communication techniques and in fully utilizingmultiple-frequency capabilities as a diagnostic element rather thanmerely as an alternative locating approach.

Portable locators that heretofore have been developed offer limitedfunctionality insufficient for quickly and accurately locating buriedutilities

SUMMARY OF THE INVENTION

An embodiment of the present invention advances the art of locatinghidden conductors, such as cables, pipes, or other lines, or dipoletransmitters such as sondes, through the integration of multiple devicesand sensors in a communication and control system known as a meshnetwork. However, the present invention may also be implemented on asystem that does not include a mesh network.

Another embodiment advantageously uses local time of flight (LTOF)positioning.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this invention, reference is nowmade to the following detailed description of the embodiments asillustrated in the accompanying drawing, in which like referencedesignations represent like features throughout the several views andwherein:

FIG. 1 illustrates a portable locating system comprising areceiver/locator (100) linked by wireless mesh connection (112) to atransmitter (102) which is inductively transmitting a signal into aburied conductor (in this case a water pipe (108).

FIG. 2 illustrates an extended mesh network in which information isshared through wireless links (220, 224, 228, 230, 232, 234) among areceiver/locator (200), an A-frame fault detection device (214), aremote geophone (216), a transmitter (202), a DGPS Base Station (204), asecond transmitter (206), a second, tripedal, locator/receiver (212), athird transmitter (208) and a more distant fourth transmitter (210).Note that any node in the network may be equipped with an InertialNavigation module to provide data about location or movement of thatunit.

FIG. 3 illustrates a single locator/receiver (300) linked via a wirelessconnection (306) to a distant transmitter (304) to which it is sending adata stream (308) which includes a “Power Off” control signal.

FIG. 4 illustrates a portable locating system comprising onereceiver/locator (400) connected via a wireless link (410) to adirectly-connected transmitter (402), and via a second wireless link(406) to a second transmitter (404).

FIG. 5 illustrates a portable locating system comprising onereceiver/locator (500) and one transmitter (502); the transmitter isconnected by direct connection (512) to the accessible section of anunderground cable (506), and alternative connection via an inductiveclamp (504) is also shown.

FIG. 6 illustrates a portable locating system comprising onereceiver/locator (600) and one transmitter (602); the transmitter (602)is connected to a water line (608) at an above-ground point by means ofa direct-connect cable (610), and is grounded by means of a groundingstake (614) to which it is connected by a similar direct-connect cable(612)

FIG. 7 illustrates the logic of a portable locating system comprisingone transmitter and one receiver in dynamically determining optimumfrequency. Signal Quality is evaluated by the receiver/locator; acontrol data stream is sent to the transmitter, instructing thetransmitter to change frequency.

FIG. 8A illustrates a portable locating system comprising alocator/receiver (800) which is linked by wireless connection (810) to atransmitter (802) which is connected by inductive clamp (804) to anaccessible portion of an underground electrical cable (806), in atypical interference situation.

FIG. 8B illustrates the procedural logic of the system group of FIG. 8A.

FIG. 9 illustrates a portable locating system comprising alocator/receiver (900) in use by an operator (904), with a wirelessconnection (906) to a distant transmitter (902).

FIG. 10 illustrates a portable locating system comprising a transmitter(1000) in use by an operator (1006) which is connected by wireless links(1008, 1010) to two distant receiver/locators (1002, 1004).

FIG. 11 illustrates a portable locating system including areceiver/locator (1100) whose display (1106) is shown in a separateblowup image, and connected by wireless link (1108) to a transmitter(1102) which is connected to an accessible portion of a water line(1104) by direct connection.

FIG. 12 illustrates a portable locating system including areceiver/locator and a transmitter in which the operator can key in forstorage data defining the type of utility to which the group isconnected (directly or inductively) and in which the receiver candisplay and/or store the utility-type with the detected signal from theparticular transmitter.

FIG. 13 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans such that part or all of the display of any element of the systemcan be displayed remotely on the display of any other element of thesystem, such as a remote portable computing device, for example.

FIG. 14 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, and in which a WAN-aware digital device (e.g., a cell phone orPDA) and a remote computer are members of the group acting as datadisplay, logging, or relay devices.

FIG. 15 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which the receiver may send instructions to the transmitter toreverse current direction.

FIG. 16 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which the data exchanged describing field angles detected at aseries of frequencies, and current and voltage values at each suchfrequency, is used in analyzing cross-coupling between adjacentutilities or conductors.

FIG. 17 a illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which the amount of cross coupling to adjacent utilities isbeing determined at a receiver by commanding a remote transmitter tosimultaneously or sequentially to transmit two or more differentfrequencies, and measuring the relative change in receiver measuredfield angles.

FIG. 17 b illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which the variation in depth measurement appearing as functionof frequency, in addition to transmitted current and voltage data, isdetermined by commanding a remote transmitter to generate twofrequencies (simultaneously or sequentially). The comparison of depthmeasurements at frequencies is used to improve the accuracy of depthmeasurement.

FIG. 18 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which self diagnostic information is exchanged andcommunicated to the receiver for calculating reliability of results anddiagnosing system failures, and which may include methods to determinefunctioning of various locator system elements.

FIG. 19 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which elements of the system are recognizing a newly addedelement of the system, a “smart” clamp, across a wireless data link.

FIG. 20 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which a transmitter experiencing low battery condition isinforming other elements of the system group of an imminent resultantshutdown.

FIG. 21 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which all clocks of the system elements are being synchronized,in this case using an optional GPS satellite time signal.

FIG. 22 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which system elements are equipped with GPS receiver, and inwhich DGPS corrections are exchanged between system elements in order toimprove relative position accuracy. Units may similarly be equipped withInertial Navigation modules to provide location and movement dataindependent of or in addition to GPS information.

FIG. 23 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which a receiver controls a transmitter to increase or reducetransmitted current in order to maintain signal strength at thereceiver. The receiver is also modulating sound gain levels at thereceiver so that they do not change when transmitter output currentchanges, thus making the process transparent to the operator.

FIG. 24 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which a phase reference timing signal is communicated by thetransmitter to the receiver. The transmitter may optionally include atime-stamp in the transmission. The transmitter may also send thecorresponding phase signal on the utility itself.

FIG. 25 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, integrated with a pipe inspection camera system using a sonde togenerate a detectable signal. Data items being communicated includingsonde depth, signal strength, cable footage count, compass angle, sondepower status, camera tilt and sonde angles, and control signals to turnthe transmitter on or off.

FIG. 26 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which a multiple-frequency capable inductive transmitter isbeing remotely controlled by a distant receiver, and information fromthe line and the transmitter are compared in order to determine thedegree of any air coupling between transmitter and receiver. Bycompensating for or correcting signal strength caused by air coupling,the system allows an operator to perform locating tasks closer to thetransmitter.

FIG. 27 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans wherein a rotating and/or tilting (not shown) mechanism isincorporated into the transmitter and its angle and degree of tilt androtation controlled from the receiver, thus enabling signals fromseparate utilities to be individually nulled, and the utilities in acomplex situation to be individually located.

FIG. 28 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which the group network is extended to include a variety ofother devices used in location and detection tasks, including ageophone, an A-frame fault detector, and a sonde of the type used inHorizontal Directional Drilling (HDD) applications. The extended networkincorporates information from GPS and/or Iridium satellites andincludes, as well, a cell-based WAN link or satellite uplink such asIridium, and a wireline link to the HDD machine. The network is extendedby a data-relay node device. Additionally, any device or node in thenetwork may include an Inertial Navigation module to providesupplementary location or movement data to the network.

FIG. 29 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which the operator uses the data-link between a transmitter anda receiver to send information to the receiver describing the nature ofthe connection made in connecting the transmitter to the utility. (Inthis example, the transmitter is connected by means of a tracer wireinstalled along the exterior of a non-conducting gas-line).

FIG. 30 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which system elements include devices other than locators andtransmitters, including a laser range finder, a GPS signal beacon, and acell-based WAN link. Information is integrated at a mapping locator inthis example.

FIG. 31 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which a ZigBee or similar wireless link connects thelocator/receiver to the transmitter, and informs the transmitter of thereceived signal strength, enabling the transmitter to emit a ping soundif it is the transmitter closest to the receiver in the mesh; theproximity of the receiver to the transmitter being determined bycomparison of the Receive Signal Strength level.

FIG. 32 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which the transmitter sends timing signals for two frequencieswirelessly, such that the presence of coupled utilities can be readilydetected by comparison of the apparent target location detected at eachof the multiplexed and time-signaled frequency transmissions. Similarly,a change in apparent depth between the time-multiplexed frequencysignals can be used as a basis for depth correction.

FIG. 33 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which the locator/receiver performs sampling of the ambientelectromagnetic frequency domain, using FFT or other methods, in orderto identify frequencies which will produce improved signal to noiseratio in the locating process; the calculated optimum frequency is thenset on the transmitter by means of a wireless control link betweenreceiver/locator and transmitter.

FIG. 34 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans in which a distant transmitter monitors the amplitudes of varioussignal peaks and harmonics and transmits computed FFT “frequency bins”to the receiver, which in turn compares and tunes its digital filtersagainst the profile of the transmitter-provided FFT data to optimize thesignal-to-noise ratio in the locating process. The use of the monitoredinformation as a “fingerprint” of the connected utility can then enablea receiver to confirm that it has detected the same utility or adifferent one. Analog-Digital Converter (ADC) information can besimilarly transmitted instead of FFT frequency bin data; transmissioncan be via ZigBee, Bluetooth, a 6LoWPAN sensor network design, or othermeans.

FIG. 35 illustrates a portable locating system in which a remote locatordisplay is relayed wirelessly to a separate projection device,displaying locator events for classroom training in near-real time,while optionally also controlling the “slaved” display on a studentreceiver/locator.

FIG. 36 illustrates a portable locating system in which a remotereceiver/locator display is sent as data via a wireless link and thendisplayed on a remote device such as a supervisor's portable computer ora training system. If the sending unit is doing passive locating, notransmitter is required.

FIG. 37 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which the transmitter includes a user interface such as adisplay or speaker, and receives signal strength information from thereceiver/locator; the operator is moving the transmitter to determinethe point at which a maximum signal or a null signal is received.

FIG. 38 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, and which include two instances of node devices used solely asrepeaters in order to extend the mesh network's range or extend itaround a signal-barrier such as a building.

FIG. 39 a portable locating system that includes at least one receiverand one transmitter that can each communicate by wireless means, andincluding a frequency-shifting re-transmitter used in conjunction withan A-Frame application and device to which the re-transmitter is docked,used in isolating a line fault in a buried utility.

FIG. 40 illustrates a portable locating system including a three-channelspatial re-transmitter used in conjunction with three geophones and atripod, four-antenna node receiver, that can each communicate bywireless means, and coordinated via wireless links for application inacoustic tomography imaging, or in isolating and locating leaks in apiping system.

FIG. 41 illustrates two portable locating systems, in which a long-rangeradio frequency link is used to join the two local mesh networks, thusextending the operation of the mesh network over longer distances.

FIG. 42 provides a detailed view of a Locating Ranging Cone, similar toan ordinary “traffic cone” and equipped with locational and networkingdevices such as a “time of flight” ranging transceiver, a GPS receiver,a GPS or magnetic compass, or a supplementary radio antenna, as requiredfor particular applications.

FIG. 43 illustrates a ranging/locating area defined by the use ofmultiple Ranging Cones in which information on ranges to various nodeswithin the area and other data is constantly being exchanged between theradio transceivers across the locating group.

FIG. 44 illustrates a similar group in which the precision of locationalinformation is augmented by use of an Inertial Navigation System (INS)module whose information is integrated with ranging data for moreprecise locational measurement.

FIG. 45 illustrates a general “time-of-flight” ranging system in whichranges among the various nodes are computed, which data could beintegrated into a typical locating group operation.

FIG. 46 illustrates a tripod locating receiver which usesground-tracking sonar sensor devices mounted on the locator's legs in anexemplary configuration showing the use of Doppler measurement inrefining locational information.

FIG. 47 illustrates a one-legged locator receiver of more traditionalform with Doppler transducers similarly mounted inside each of thegradient coil antennas on either side of the locator shaft.

FIG. 48 illustrates a locator equipped with a type of sonar transducerarray known as a correlation sonar array, which provides even finerdisplacement measurement of movement over the ground, such as by alocator receiver in use.

FIG. 49 illustrates an example of locating receiver equipped with aportable display and communication device attached to it by means of acable interface providing power and data; such a device is similar to aPDA or advanced cellular phone, for example, providing display, storage,and connectivity for data transmission by wireless means.

FIG. 50 illustrates a portable display and communication device used atleast in part, as the display and user interface system for a video pipeinspection system. Such a pipe inspection system may be a participatingunit in a mesh network locating group, or may operate independentlyaccording to need.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The entire disclosures published U.S. Patent Application No.2004/0070535 A1 entitled “Single and Multi-Trace Omnidirectional Sondeand Line Locators and Transmitter Used Therewith,” filed Dec. 3, 2002,of Mark Olsson et al. and pending Ser. No. 10/956,328, filed Oct. 1,2004, entitled “Multi-Sensor Mapping Omnidirectional Sonde and LineLocators,” of Mark Olsson et al. are incorporated herein by reference.

This invention provides an improved cable, pipe and sonde (dipoletransmitter) locator method and technology that may consist of a localmesh network of devices exchanging information and control streams asrequired, or a sophisticated stand-alone system with integral datagathering and processing subsystems.

In these embodiments, the basic guiding concept is to enable allfunctional units of a utility locating system with wirelesscommunication capability. The top level concept is that these elementsare each part of a system that must function together. Generally, thisrequires an operator to supervise the coordination of the various partsof this system which adds complexity and severely limits the degree ofsystem coordination possible. Typical elements of such a locating systemare various types of receivers and transmitters and related accessoriessuch as Sondes, clamps, A-frames, stethoscopes etc. In addition to thecore intelligence necessary to participate in a mesh network, eachdevice is equipped with device-specific intelligence enabling it to sendand receive appropriate data items through a meshed “publish andsubscribe” approach. Devices “publish” their data items wirelesslymaking them accessible to any other device on the network; individualdevices “subscribe” only to those data items which are “of interest” tothem in the execution of their functions, an attribute which is definedby the software programming of the device.

The basic idea of the present invention is to enable all functionalunits of a utility locating system with wireless communicationcapability. The top level concept is that these elements are each partof a system that must function together. Generally, this requires anoperator to supervise the coordination of the various parts of thissystem which adds complexity and severely limits the degree of systemcoordination possible.

Typical elements of such a system are various types of receivers andutility transmitters and related accessories such as Sondes, clamps,A-frames, stethoscopes etc. In general, each of these devices, designedto be used alone or in conjunction to a single utility transmitter only,will introduce problems in the accuracy and repeatability of itsresults, especially in complex situations where multiple conductors (as,parallel pipes or wires in a conduit, for example) are involved. Thepresent invention offers a remedy to this generic shortcoming byenabling the correlation of key information from multiple devices; byenabling multiple-frequency comparisons in the refinement of depthdetermination and location of target conductors (pipes, wires, cables,etc.); and by enabling the internetworking of locating devices to remotesystems for observation, training, cross-correlation with geographicalinformational systems, and supervision of the locating process.

In a mesh network, multiple devices act as nodes, each of which iscapable of connecting with any other node. A node is defined for thispurpose as a device which can send data to or receive data from anothercomponent or node in the network. A mesh network is a set of nodes eachof which can communicate to any other, either directly or via othernodes in the mesh. Because each node in a mesh network is capable ofreceiving and sending data, it can act as a repeater or as a router. Arepeater is a node which re-broadcasts received data and command signalsbut takes no other action on them, serving only to extend or reinforcethe communication channels of the network. Mesh networking provides forcontinuous connections and reconfiguration by hopping from node to nodeuntil a desired connection is established. Mesh networks therebyaccomplish a high degree of flexibility and self-healing compared toeither wired networks or rigidly configured wireless networks. Deviceswhich may act as nodes, according to the present invention, may includemultiple utility transmitters, locator/receivers, sondes,fault-detection devices, geophones, ground-penetrating radar devices, orother devices related to the activity of locating underground utilitiesor hidden objects. Mesh networks can be established by various wirelesscommunication means, of which the ZigBee protocol is a paradigmaticexample. In addition, local meshes may be joined through the use of along-range radio-frequency link thus extending the informational networkover long distances.

In the present invention, the broadcasting (from a node) of informationwhich it has is known as “publishing.” The listening (by a node) forparticular information needed is known as “subscribing” to thatinformation.

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby information can be relayed bymesh networking means from one member of the portable locating system toanother thus increasing possible communication distance. (Ref. FIG. 1)

According to one aspect of this invention, the requirements for wirelessconnection are achieved using low-power wireless personal area networkdevices (LoWPAN) using IEEE 802.15.4 standard links carrying IPv6communications, a method known as 6LoWPAN.

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby each communicating member ofthe locating system acts as a node in a mesh network allowinginformation to be sent from node to node to extend the physicaltransmission range beyond the maximum direct point to point transmissiondistance. According to this aspect, any element of the system can act asa network mesh (router) element and relay information on to othernetwork node elements. This is particularly useful in situations where anetworks range needs to be extended. To this end, additionaltransceiver(s) could be placed in a network with the sole intent ofusing them to extend the range of the network, without using them as“utility transmitters” for location. Typical elements of such a systemare various types of receivers and utility transmitters and relatedaccessories such as Sondes, clamps, fault finding A-frames, conductoridentifying stethoscopes, geophones for leak detection and undergroundimaging purposes etc. Each device would “Publish” its status bybroadcasting periodically for other devices to “Subscribe” to, orignore. This method obviates any need for one device to interrogateanother device for information (Ref. FIG. 2).

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby utility transmitters can beturned off and on remotely from a receiver. (Ref. FIG. 3)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby any device in the system cansend operational status and/or control signals to any or all othermembers of the system group. One or more members of the portablelocating system can be turned off and on and otherwise controlled fromany communicating device that is part of this group. (Ref. FIG. 4)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby a utility transmitterconnected to a utility measures the impedance of the connection and usesthis information to determine a desired transmit frequency and thenwirelessly communicates that frequency to other members of the portablelocating system. The utility transmitter might also optionallycommunicate utility impedance information. The utility transmitter mightalso optionally become active at the frequency and begin to transmitthat frequency. The utility transmitter might be connected directly orinductively to the utility. (Ref. FIG. 5)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby a utility transmitter thatdetermines the impedance characteristics of the circuit it is connectedto, measures how the impedance of this circuit responds to changes infrequency, and uses this information to automatically determine whichfrequency to use and then broadcasts this information onto the network,where the receiver would detect this status information. The receiverthen automatically configures itself to this frequency. The feature isimproved by providing switchable tuning elements, so that the impedance(and admittance) of the line are nearly pure real. Series and shunt,capacitors and inductors can be used. The difference in phase betweenthe current and the voltage delivered to the utility can be measured todetermine the capacitive or inductive nature of the utility in responseto the applied signal. (Ref. FIG. 6)

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means, whereby a locating system where theoptimal frequency is determined dynamically, and wherein higher or lowerfrequencies are enabled during the locating process to determine ifsignal quality can be improved. An example of this process is whereSignal A is being broadcast by the transmitting device and received bythe receiving device. Signal B is then broadcast simultaneously orseparately for a short period of time and the signal characteristics arecompared to those for Signal A. If one of the locating device elementsdetermines that Signal B offers better locating characteristics, thenthe locating system can either switch automatically, or post a messageto the user interface and offer to switch to a new operating frequency.This automatic behavior can be made completely transparent to theoperator if desired, in the simplest mode of operation. (Ref. FIG. 7)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby a receiver detecting atransmitted frequency commands the utility transmitter to changetransmitted frequency to reduce interference from other signals andthereby improve the detected signal stability or the signal to noiseratio of the detected signal. This is one form of jammer avoidance.(Ref. FIG. 8)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby when the active receiverfrequency and associated processed data that is being displayed to theoperator is changed under operator control to a different operatingfrequency that the utility transmitter will also switch frequency tofollow this active receiver frequency. (Ref. FIG. 9)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby when the active transmitfrequency being broadcast and coupled onto a utility is changed underoperator control or automatically under processor control from eitherthe utility transmitter or the receiver to a different transmittedfrequency that one or more receivers will also switch frequency tofollow this active transmitter frequency. (Ref FIG. 10)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby the utility transmitterbroadcasts the current it is sourcing into the utility that it isconnected to and the receiver uses this information to display thesensed, measured current as some fraction or percentage of the totalcurrent sourced by the utility transmitter. (Ref. FIG. 11)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby when the operator connects autility transmitter to a utility the operator can communicate the typeof the utility (e.g. gas, water, power etc.) to which the connection ismade to the user interface in either the utility transmitter or thereceiver thus enabling the receiver to display to the operator andoptionally store the type of utility associated with the detected signalfrom a particular utility transmitter within the locating system group.(Ref. FIG. 12)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby all or any part of thedisplay or the information associated with the display of any locatingsystem element can be remotely shown by any other element of the system.(Ref. FIG. 13)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby any remote computing means(e.g. a PDA or a computer or a Bluetooth enabled cell phone) can act asa member of this portable locating system and act as a remote displaydevice or data relay or data logging device. (Ref. FIG. 14)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby current direction coding at autility transmitter can be reversed by a command from a receiver. (Ref.FIG. 15)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one utility transmitter that caneach communicate by wireless means whereby the amount of cross couplingto adjacent utilities can be determined at a receiver by commanding oneor more remote utility transmitters to change to one or more differentfrequencies and measuring the relative change in receiver measured fieldangles; and optionally, to send current, voltage and impedance valueswith each. A coupling or distortion warning can be optionally displayedon the receiver to alert the user. By way of example, two transmittersmight be commanded by the receiver to swap broadcast frequencies. (Ref.FIG. 16)

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means, whereby the amount of cross coupling toadjacent utilities can be determined at a receiver by commanding aremote transmitter to simultaneously or sequentially transmit two ormore different frequencies, and measuring the relative change inreceiver measured field angles at one or more antenna locations. Acoupling or distortion warning can optionally be displayed on thereceiver to alert the user. (Ref. FIG. 17 a)

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby the variation in depth measurementas a function of frequency can be determined at a receiver by commandinga remote transmitter to simultaneously or sequentially to transmit twoor more different frequencies and measuring the relative change inreceiver measured depth. The information can be used to extrapolate thedepth measurement to zero frequency to provide an improved accuracydepth measurement. If three or more frequencies are used then themeasurements can be compared to a skin depth model and variations inground return current due to local variations in soil conductivity canbe ascertained. (Ref. FIG. 17 b)

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby self diagnostic information can beexchanged and communicated between system elements. (Ref. FIG. 18)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby newly detected system elements canidentify themselves to the other elements in the system and also provideinformation about all of their capabilities to the rest of the system. Atransmitter for example can know that it is hooked to a certain type ofclamp and can communicate that information to the receiver to allow afull audit of the locating process to be stored. (Ref. FIG. 19)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a transmitter or other systemmember notifies other system elements that its batteries are nearlyexhausted and warns of an impending shutdown. (Ref. FIG. 20)

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby all clocks, including real timeclocks present in system elements can be synchronized in time. Any onecommunicating system element can serve as a master clock. Any onecommunicating system element with available external clock such as GPStime can serve to synchronize system clocks to an external timereference. (Ref. FIG. 21)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby any system member may have a GPSreceiver allowing DGPS corrections to be made, exchanged and or storedbetween system elements and the relative position accuracy improved. Inaddition, any unit may be equipped with an Inertial Navigation module toprovide location or movement data independent of or supplementary to GPSinformation. (Ref. FIG. 22)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby the receiver commands atransmitter to only source the amount of current needed for a strong andstable signal thereby conserving available battery energy. Operatorintervention is not required and this process may be transparent to theoperator. Additional to this aspect is the automatic adjustment of thesound gain level, such that changes in output current do not causechanges in sound level (Ref. FIG. 23)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a phase reference timing signal issent from the transmitter to the receiver for the purposes ofdetermining relative phase of the transmitted signal at the receiver.(Ref. FIG. 24)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means and used in conjunction with a pipeinspection camera system that was similarly enabled. The camera systemsends the locator the pushcable count and the receiver sends the camerasystem the measured Sonde signal strength and/or line depth. Optionallyif the camera system was equipped to determine the signal strength ofits Sonde, then the Sonde signal strength information can be sent to thereceiver and the combined pipe-ground signal attenuation characteristicscan be determined. As the locator is walked along the pipe as the sondeis pushed, the depth of the pipe can be displayed and recorded on thevideo. If a transmitter can be turned off and on, this function couldalso be controlled from the locator, avoiding the problem of needed toreturn to the camera controller to turn on the transmitter. Optionally,if the locator is equipped with a compass, the orientation of the piperelative to true or magnetic north can be recorded on the video.Additionally, if the locator was navigated the route and depth of thepipe can be mapped. (Ref. FIG. 25)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a multi-frequency utilityinduction transmitter can be remotely controlled and switched betweentwo frequencies. The degree of air coupling can be determined becomparing how the received signals change as a function of frequency.The air coupling can be accurately determined and can be subtracted fromthe received signal data and the degree of air coupling can thereby bereduced. This allows the operator to locate hidden utilities closer toan inductive dipole source. One or more transmitter source magneticfield strengths can be measured internally at the transmitter andtransmitted by wireless means to one or more receivers. (Ref. FIG. 26)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a rotating or tilting meansremotely controlled from the receiver by said wireless means is placedunder or integrated into an inducing transmitter. The inducingtransmitter is rotated and/or tilted until the signal on a target lineis minimized or nulled, allowing adjacent nearby utility lines to beseparately located. (Ref. FIG. 27)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a locating system wheretransmitters are not limited to EM devices (conducted, coupled orinduced), but could also include acoustic receivers or transmitters, orother types of transmissions as might be used in utility location andleak detection, directional drilling, or other related tasks. Thesewould be able to connect to this same network, and would likewiseperiodically transmit their status. According to one aspect of thepresent invention, a portable display and communication device is usedat least in part, as the display and user interface system for a manportable pipe and cable locating system. According to one aspect of thepresent invention, a portable display and communication device is usedat least in part, as the display and user interface system for a videopipe inspection system. (Ref. FIG. 28)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby when the operator connects atransmitter to a utility the operator can communicate the type of theconnection point (e.g. pipe, tracer wire, transformer, valve, meteretc.) to which the connection is made to the user interface in eitherthe transmitter or the receiver thus enabling the receiver to display tothe operator and optionally store the type of utility connection pointassociated with the detected signal from a particular transmitter withinthe locating system group. The communication from the operator to theuser interface of either device can be made by any known means includingbut not limited to keypad, touch screen or voice input (Ref. FIG. 29)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a locating system where devicesother than locators and transmitters can be networked, including standalone GPS receivers, acoustic or laser range finding devices, mappingbeacons, or computers which could allow monitoring and/or recording ofthe locate and optionally allowing transmission of the location data inreal time or post process to other computers via internet or othernetwork. (Ref FIG. 30)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a locating system where theproximity of a transmitter to a locator can be roughly determined byReceive Signal Strength Indication or other means, to allow for specialbehavior—such as (for instance) having an acoustic pinger active on onlythe nearest transmitter, so that a user could more easily identify itslocation, or using that proximity to indicate a special icon on the userinterface of the locator. (Ref FIG. 31)

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a transmitter can time multiplexits output between two or more frequencies and the timing signals can besent wirelessly to maintain synchronization between the two devices. Inparticular, using narrow band short time constant (or FIR) filters infront of a correlation based receiving channel the output of atransmitter might be rapidly switched between two different output modesand the receiver would be relatively insensitive to phase shifts. If theapparent position of a utility changes appreciably at differentfrequencies then other coupled utilities are present. If the depth movedvertically between the different frequencies, then a depth correctionmay be required. (Ref. FIG. 32)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby the ambient electromagneticenvironment can be sampled in the frequency domain by an FFT or othermethods known in the art. This information can be used to identifyfrequencies that will provide improved signal to noise and thetransmitter can be commanded to transmit at one or more of theseidentified frequencies. (Ref. FIG. 33)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby the amplitudes of various signalpeaks or harmonics can be monitored in real time by a receiver at aremote location to serve as a “fingerprint” of a given utility. Thisinformation can then be transmitted to another receiver which candetermine if it is locating the same utility. Alternately, if adequatebandwidth is available a copy of the signal can be transmitted andcross-correlated in the second receiver. ADC data can be transmitted viaZigBee, Bluetooth or other means. Alternately, FFT frequency bin datacan be transmitted. (Ref. FIG. 34)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a remote locator display isenabled on a separate device; for example, in displaying locator eventsfor classroom training in real time or near-real time. (Ref. FIG. 35)

According to one aspect of this invention a portable locating systemthat includes at least one receiver that can each communicate bywireless means and a remote locator display is enabled on a separatedevice, such as a remote computer used in training or supervision oflocator activity. During passive locating, no transmitter is required.(Ref. FIG. 36)

According to one aspect of this invention a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby a user interface, perhaps aspeaker, was present in a Q-ring, then a receiver could be placed over aknown line and transmit an indication of its received signal to aremotely located Q-ring being manipulated by an operator to eithermaximize or null an induced signal as desired. This can be done with asingle operator. (Ref. FIG. 37)

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one transmitter that can eachcommunicate by wireless means whereby the mesh network of devices in thegroup may be extended in range by the use of a node device whose solepurpose is extending the range mesh network. For example, a node devicemight be used to enable a mesh network to communicate around an obstaclewhich would otherwise prevent network connection from being reliablyestablished such as a metallic shed (Ref. FIG. 38).

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one frequency shifting signalretransmitter that can each communicate by wireless means. (Ref. FIG.39)

According to one aspect of this invention a fault finding portablelocating system that includes at least one receiver and one frequencyshifting retransmitter that can each communicate by wireless meanswhereby the frequency shifting retransmitter is mounted onto a structurewith two or more ground contacting probes measuring time varying voltagepotentials in the ground. A circuit means in the frequency shiftingretransmitter amplifies and frequency shifts and then retransmit saidtime varying voltage potentials via an antenna coil. The receiverdetects said retransmitted signals and determines a signal that relatesto the time varying voltage potentials in the ground. (Ref. FIG. 39)

According to one aspect of this invention, a portable locating systemthat includes at least one receiver and one spatially distinctmulti-channel signal retransmitter that can each communicate by wirelessmeans. Up to three distinct signals can be transmitted from collocatedorthogonal coil antennas and these signals can be separated intodistinct channels at the receiver. A rotation matrix can be applied tothe incoming data to optimize alignment of each orthogonal transmittedsignal into a receiving coordinate system where each axis is nominallyaligned with the transmitted signals. Reference tones can be optionallybroadcast on each channel to facilitate the coordinate alignmentprocess. Channel to channel cross-correlation can also be minimized, inorder to maximize channel separation. (Ref. FIG. 40)

According to one aspect of the present invention, a long-range radiolink may join at least one member in each of at least two shorter-rangemesh networks, which themselves use a mesh network-capable communicationprotocol such as ZigBee-enabled or 6LoWPAN network links. Thus, multiplemeshes may be joined over longer distances by using a long-range linkintegrated into one or more members of individual mesh networks,effectively using them as subnets. The long-range link may beestablished using a cell-phone link or other long range wireless, RF,microwave, fiber-optic, or wired communication means, with mesh-enableddevices at either end of the link serving to join the local meshnetworks. (Ref FIG. 41)

According to one aspect of this invention, a network of locating-relateddevices may include a ranging and locating beacon, a portable object inwhich ranging transceivers, such as those utilizing “time of flight”computation to compute distances between network nodes, may be mounted,and which may incorporate in their structure other sensors such as a GPSreceiver, GPS or magnetic compass, a magnetic dipole beacon or otherdevice for use in generating locational information. (Ref. FIG. 42.)

According to one aspect of this invention, a series of such beacons maybe deployed to create a locating ranging area, using (for example)“time-of-flight” wireless ranging to establish ranges to the severalcorners of the area as defined by such beacons, with a similar rangingtransceiver being mounted on a mobile locator whose position isconstantly being similarly computed. (Ref. FIG. 43)

According to one aspect of this invention, any node in a locating groupor network may be equipped with an inertial navigation system (INS)module. In this configuration, the INS may be used to provide refineddisplacement measurements from which to enhance the precision of a“time-of-flight” ranging system described above. (Ref. FIG. 44.) Ingeneral, any devices acting as nodes in such a group may be equippedwith transceivers used in “time-of-flight” ranging calculations. (Ref.FIG. 45). Point-to-point time of flight positioning using an array of atleast two fixed transceivers and one mobile transceiver operatesindependently of other kinds of communication among devices andindependent of mesh network participation or non-participation.

According to one aspect of the present invention, locational informationon moving devices may be provided by Doppler transducers known asground-tracking sensors; for example, a locator may have such sensorsmounted on its legs or its shaft to provide precision displacementinformation as it moves over the ground. (Ref. FIGS. 46 and 47). Inanother aspect of the present invention, a locator or other movingdevice may be equipped with a Doppler array known as a correlation sonararray to measure fine displacement and compensate for drift in otherlocational devices in the network. (Ref. FIG. 48).

According to one aspect of this invention, a pair of temperaturecalibrated oscillators is used in a transmitter receiver pair to improvethe relative time accuracy allowing the absolute phase of thetransmitter's output to be known by the receiver. A relative accuracy of1 millisecond per day can be thusly achieved. A known positionalrelationship, phase encoding, a wireless link or other means can be usedto synchronize these clocks.

According to one aspect of this invention absolute phase information istransmitted from the transmitter to the receiver by a wireless linkwhich allows the receiver to determine if the received signal from aburied utility is in phase or out of phase with the signal transmittedby the line transmitter.

According to one aspect of this invention, while the mobile unit isstationary for some period of time, three orthogonal low driftgyroscopes are used to determine true north due to the rotation of theearth. High performance fiber optic ring gyros can be used to establishtrue north within approximately 5 minutes of elapsed time in astationary position. The precision can be obtained to within one onehundredth of a degree. If an accurate vertical reference is available,the mobile unit does not need to be held stationary in order toestablish a true north heading.

According to one aspect of this invention, Maximum Likelihood Estimators(MLE) and Maximum Entropy Method (MEM) to this filing are used toprovide a precise location for the utility in the presence of noise.This is a statistical process. MLE can suck up the navigation sensorinformation and the antenna information and provide the best estimate ofthe location of the utility without explicitly having a Kalman filter.Optionally a Weiner filter can be used.

According to one aspect of the present invention, a portable display andcommunication device is used at least in part, as the display and userinterface system for a man portable pipe and cable locating system.According to one aspect of the present invention, a portable display andcommunication device is used at least in part, as the display and userinterface system for a video pipe inspection system. (Ref. FIG. 49, 50).

For the purposes of navigating or providing positional information, thespecific configuration of a MESH network is not absolutely necessary tothe operation of networked locating groups. A mesh network is aparticular type of network where data can be passed from node to node,perhaps via several different paths. Other networking methods andtopologies may be used as suitable to the devices in the group.

Systems Elements

In accordance with an embodiment of our invention, a transmitter forinductively or directly applying a tracing signal to a hidden utility isprovided with a wireless link that periodically broadcasts its currentstatus which might include, for example:

-   -   Transmit Frequency    -   Transmit Current and Voltage    -   Connection Complex Impedance    -   Available Frequencies    -   Model and Serial Number    -   Remaining Battery Capacity    -   Attached Accessories in Use    -   Real Time Clock    -   GPS Position    -   Relative Time of Fight Position radio, light or acoustic    -   Inertial Navigation Unit locational or movement data    -   Attitude and Orientation    -   Temperature    -   Clocking or Timing Pulses    -   Transmission Codes    -   Modulation technique    -   Available Modulation techniques    -   Device status such as “Active” or “Powering off” or “sleeping”

In accordance with an embodiment of the present invention, a receiver isprovided with a wireless link that periodically broadcasts its currentstatus which might include, for example:

-   -   Active Receiving Frequencies    -   Electromagnetic Vector Information    -   Available Frequencies    -   Model and Serial Number    -   Remaining Battery Capacity    -   Attached Accessories in Use    -   GPS Position    -   Inertial Navigation Unit locational or movement data    -   Attitude and Orientation    -   Inertial Status    -   Temperature    -   Height above the Ground    -   Modulation technique    -   Available Modulation techniques    -   Device status such as “Active” or “Powering off” or “sleeping”    -   Relative Time of Flight Position, radio, light or acoustic

Devices quipped with said transmitters and receivers used in thelocating industry, including, for example, frequency transmitters,locator/receivers, geophones, fault-locating devices, GPS Base Stations,network node relay devices, etc. capable by reason of being so equippedof forming mesh networks in which the network elements identify,transmit information to, and receive information from each other in adynamic, self-maintaining configuration defined in each instance by thedevices involved and their requirements. An instance of a set of suchdevices is referred to herein as a portable locating system. Such agroup may include “time of flight” ranging transceivers enabling thegroup devices to measure their relative distances to each other, sonardisplacement measuring devices using Doppler calculations, or othermethods of determining their relative locations or their geographicallocations.

FIG. 1 illustrates a portable locating system comprising a man portablereceiver/locator (100) linked by wireless mesh connection (112) to atransmitter (102) which is inductively transmitting a signal into aburied conductor (in this case a water pipe (108). The inductivetransmitter (102) is connected through another wireless link (114) tosecond transmitter (104) which is directly connected through a cable(116) and clamp (118) to an accessible hydrant (106) leading to theburied pipe (108). The directly connected transmitter is also connectedto a ground stake (110) via a second cable (120). Information regardingthe sensed impedance of the buried connector and the frequency used bythe direct-connect transmitter (104) is relayed to the inductivetransmitter (102) through a wireless link (114), while receiverinformation is relayed to both transmitters (102, 104) from thereceiver/locator (100) in the mesh network via wireless links (112,114).

FIG. 2 illustrates an extended mesh network in which information isshared through wireless links (220, 222, 224, 226, 228, 230, 232, 234)among a receiver/locator (200), an A-frame fault detection device (214),a remote geophone (216), a transmitter (202), a DGPS Base Station (204),a second transmitter (206), a second, tripod, locator/receiver (212), athird transmitter (208) and a more distant fourth transmitter (210). InFIG. 2, the various transmitters (202, 206, 208, 210) may be used purelyas mesh network nodes for the sending and receipt of information.Depending on the circumstances of the locate task, they may beindividually turned on or off as transmitters by remote signal from anoperator using one of the locators (200, 212). The operator may includethe desired frequency and power level of transmission in his commandmessage.

As in other illustrations, each mesh-network-aware device in FIG. 2 cansend and receive information, act as a network router, and provide datadefining its own identity, state, and attributes relating to its ownfunctions. For example, the A-frame fault detection unit would provide,in its broadcast information, data describing its sensor responses; theDGPS unit would provide, in its broadcast information, data describingcorrected time and location signals, and so on. Although each device mayreceive and relay any data in the mesh network cluster, it wouldotherwise ignore data items which were not of interest to it by reasonof its application-layer programming. Thus, for example, while atransmitter would publish the frequency at which it was transmitting (ifon), that information would not be subscribed to by a DGPS Base unit,being of no interest; but it would be subscribed to by a locatorreceiver in order to enable it to set itself to the appropriatefrequency. In its operation as a node, any device may relay any datawhether it uses that data in its own application layer responses or not.

FIG. 3 illustrates a single locator/receiver (300) linked via a wirelessconnection (306) to a distant transmitter (304) to which it is sending adata stream (308) which includes a “Power Off” control signal. Thelocator (300) is linked as well via a second wireless connection (310)to a second distant transmitter (302) in the other direction, to whichit is sending a separate data stream (312) including a “Power Off”control signal.

FIG. 4 illustrates a portable locating system comprising onereceiver/locator (400) connected via a wireless link (410) to adirectly-connected transmitter (402), and via a second wireless link(406) to a second transmitter (404). In FIG. 4, the first transmitter(402) is publishing information (412) including its model number, serialnumber, present current output (100 mA), signal voltage (22V), presentbattery voltage (10.6V) and operating frequency or frequencies (here,8192 Hz and 1027 Hz). It is also publishing (412) its current statuswith regard to connection (Direct Connect=ON), its GPS location and itslocal temperature. The receiver/locator is publishing information (408)including its model and serial number, the current sensor measurementson three signal channels, the values of three axes from an internalcompass (i, j, and k) and the instrument's own orientation or tilt (q,r, and s). In addition the locator (400) is relaying to the secondtransmitter (404) an addressed control string instructing it to set itsfrequency to 32,768 Hz, and set its mode to “Inductive Output=On.” Thenodes in the group may also contain Inertial Navigation modules toprovide locational information.

FIG. 5 illustrates a portable locating system comprising onereceiver/locator (500) and one transmitter (502); the transmitter isconnected via direct connection (512) to the accessible section of anunderground cable (506). In FIG. 5, the transmitter (508) is publishingdata (510) which includes frequencies which it has tested, the detailsof its current state, and the impedance (z) and phase (+20) of the line(508). It is also publishing a control string instructing the locator(500) to use a frequency of 8,192 Hz. Alternate connection by means ofan inductive clamp (504) is also illustrated.

FIG. 6 illustrates a portable locating system comprising onereceiver/locator (600) and one transmitter (602); the transmitter (602)is connected to a water line (608) at an above-ground point by means ofa direct-connect cable (610), and is grounded by means of a groundingstake (614) to which it is connected by a similar direct-connect cable(612). FIG. 6 portrays the logical sequence which occurs when thetransmitter tests impedance measurement at several frequencies (606 a),selects the optimal frequency (606 b), optimizes its output by adjustingoutput impedance (606 c), and transmits (publishes) its resultant status(606 d). Information (618) published by the transmitter (602) includesits identity, active frequency setting, impedance value, current leveland voltage (618). The figure illustrates that the impedance measured intesting in order to calculate the optimal frequency may havecapacitative (620), resistive (622), or inductive (624) components.

FIG. 7 illustrates the logic of a portable locating system comprisingone transmitter and one receiver in dynamically determining optimumfrequency. Signal Quality is evaluated by the receiver/locator; acontrol data stream is sent to the transmitter, instructing thetransmitter to change frequency. The resultant circuit is compared atthe locator/receiver with the signal quality of the earlier circuit.This process is repeated until the best available (optimum) circuit isestablished.

FIG. 8A illustrates a portable locating system comprising alocator/receiver (800) which is linked by wireless connection (810) to atransmitter (802), which is connected by inductive clamp (804) to anaccessible portion of an underground electrical cable (806). FIG. 8Aillustrates a typical situation which would involve interference betweenthe conductor of interest (806) and distortion or cross-talk (808) fromnearby power lines. FIG. 8B illustrates the procedural logic (812) bywhich, in the present invention, the receiver (800) detects interference(812 a), transmits a command (812 b) to change frequency to thetransmitter (802) and evaluates the resultant signal quality (812 c),repeating as needed to achieve the optimal available circuit andimproving the circuit's signal-to-noise ratio.

FIG. 9 illustrates a portable locating system comprising alocator/receiver (900) in use by an operator (904), with a wirelessconnection (906) to a distant transmitter (902). In FIG. 9, the operatorin response to the data displayed on the locator (900) inputs afrequency change command to shift receiver frequency to 8,192 Hz. Acontrol data stream (910) is sent by the receiver/locator to thetransmitter to change frequency to the same frequency as that to whichthe locator is changing.

FIG. 10 illustrates a portable locating system comprising a transmitter(1000) in use by an operator (1006) which is connected by wireless links(1008, 1010) to two distant receiver/locators (1002, 1004). In FIG. 10,the operator inputs a frequency change at the transmitter (1000) to 128Hz. The transmitter then sends control data streams (1008, 1010) to eachof the receiver/locators instructing them to change frequency to 128 Hz.

FIG. 11 illustrates a portable locating system including areceiver/locator (1100) whose display (1106) is illustrated in aseparate blowup image, and connected by wireless link (1108) to atransmitter (1102) which is connected to an accessible portion of awater line (1104) by direct connection. In FIG. 11, the transmitter(1102) is publishing information (1112) defining its current output(128.5 mA). The receiver/locator (1100) is subscribing to this data andshowing a computed value on its display (1106) reflecting the ratio as apercentage between its measured current and the total current sourced bythe transmitter. FIG. 11 also illustrates the logic of the process inregistering the measured current (1110 a), comparing it to a value ofthe transmitter's published current value (1110 b) and determining theresultant ratio as a percentage (1110 c) which is then shown on thedisplay (1106).

FIG. 12 illustrates a portable locating system including areceiver/locator (1220) with an integrated LCD display (1224) and ameans of data storage (1228) internal to the receiver/locator (1220),the whole being connected via a wireless data link (1222) to atransmitter (1200) with an integrated display (1216). The transmitter isconnected to a ground stake (1210) by means of one of its cables (1212)while the other cable (1204) is directly connected by means of a clip(1206) to the accessible portion of a water utility (1202). In FIG. 12,the transmitter is equipped with a key pad (1218) by means of which theoperator may enter data indicating the type of utility to which thetransmitter is connected; the entered data is communicated to thereceiver (1220) by means of the data link (1222) and displayed (1226) onthe LCD display (1224). The utility-type data may also be stored at thereceiver's data storage device (1228) and associated with signalstrength or other information received by the receiver/locator (1220).

FIG. 13 illustrates a portable locating system comprising one or morereceivers/locators (one shown—1300) mounted on an example vehicle (1312)which carries an electronic device serving as a remote display (1308). Awireless data link (1314) connects the mounted receiver/locator with theremote display device (1308). A second wireless data link (1316)connects a second remote receiver/locator (1302) with the remote displaydevice (1308). By entering commands on the display device keypad (1306)the display can be set to display the local display (1310) data from theremote receiver/locator, or the local display (1304) data from thevehicle-mounted receiver locator (1300), or both. In FIG. 13, the remotereceiver/locator could be ordered by an operator to display the datafrom the local display on the mounted unit (1304) equally well, and theoperator at the display unit (1308) could use the data link (1314) tothe mounted receiver/locator (1304) to set it to display the displaydata (1310) from the remote receiver (1302), should he so decide.

FIG. 14 illustrates a portable locating system comprising areceiver/locator (1400) being controlled by an operator (1402) who isequipped with a WAN-linked digital device (PDA) (1404) with its own datadisplay (1408). The PDA could equally well be an appropriately designedBluetooth-enabled cell phone. The PDA (1404) is linked via wirelessconnection (1418) to a satellite (1410) and by another wirelessconnection (1422) to a cell-phone tower (1412). An additional systemelement is a remote computer (1414) which also has wireless connection(1424) to the cell tower (1412) via an integrated modem, or a separateconnection to the same satellite relay (1410). In FIG. 14, the remotecomputer (1414) can act as a remote display (1416) of data generated atthe receiver/locator (1400). Instructions entered on remote computer(1414) can be transmitted via wireless data links and displayed on thePDA Display (1408) or on the Locator Display (1406) so that a remoteoperator (1426) can convey instructions to the local operator (1402).

FIG. 15 illustrates a portable locating system comprising a transmitter(1500) directly connected to a water utility line (1504) andcommunicating to a distant receiver/locator (1502) via a wireless link(1510). In FIG. 15, the receiver/locator is sending a commandinstruction (1508) to reverse the current code direction of currentbeing placed on the utility conductor (1504) from direction code 1 (1506a) to direction code 2 (1506 b).

FIG. 16 illustrates a portable locating system comprising areceiver/locator (1600) which is communicating via a wireless data link(1614) to a transmitter (1602) which is coupled by means of an inductiveclamp (1608) to a primary utility line (1604). In FIG. 16, the primaryconductor (1604) on which the transmitter is placing current is coupledto a secondary utility line (1606) by reason of proximity. The twoconductors are coupled by an element of induction (1610 a), an elementof resistance (1610 b) and an element of capacitance (1610 c) betweenthem. In FIG. 16, the locator/receiver (1600) commands the transmitter(1602) via the wireless data link (1614) to change to a number offrequencies in sequence (1612)—128 Hz, 1024 Hz, 8192 Hz, and 32768 Hz.The receiver/locator then performs an analysis (1616) of the antennafield angles and depth data detected for each frequency used by thetransmitter (1602) in order to determine the degree of cross couplingbeing encountered. At the operator's option, a “distortion warning”(e.g., 1618) may be displayed indicating that coupling is occurring maybe displayed at the receiver/locator (1600) user interface. If two ormore transmitters are in use (not shown), different frequencies may betransmitted on different utilities or conductors.

FIG. 17 a illustrates a portable system group comprising a transmitter(1700) capable of emitting multiple frequencies, connected via aninductive clamp (1704) to a utility conductor (1706), and connected viawireless link (1710) to a distant receiver/locator (1702). In FIG. 17 a,the command is sent to the transmitter (1700) to transmit two or moredifferent frequencies (1708 a and 1708 b). Transmitter (1700) publishesfrequency, current, voltage and impedance data. The receiver can thendetermine the amount of cross coupling to some adjacent utility bymeasuring the measured field angles of detection for the frequencies andcomparing them. A distortion warning could then be displayed (as shownin FIG. 16).

FIG. 17 b illustrates a portable system group comprising a transmitter(1700) capable of emitting multiple frequencies, connected via aninductive clamp (1704) to a utility conductor (1706), and connected viawireless link (1710) to a distant receiver/locator (1702). In FIG. 17 b,the receiver/locator (1702) has issued a command to the transmitter(1700) to transmit three frequencies, either simultaneously orsequentially (1750 a, 1750 b, and 1750 c). For each frequencytransmitted by the transmitter (1700), a depth calculation is performedby the receiver/locator where:

-   -   K=the distance between the upper antenna (1760) and the lower        antenna (1758) of the locator/receiver (1754) and    -   C=the distance from ground level to the center of the lower        antenna (1756) and    -   Top B=signal value at the upper antenna (1760) and    -   Bottom B=signal value at the lower antenna (1758) and        Depth=K(Top B)/(Bottom B−Top B)−C

This calculation yields a separate value for the depth at each frequency(1752 a, 1752 b, 1752 c). The relative change in depth calculationresult can be used to provide improved accuracy in measured depth.

FIG. 18 illustrates a portable locating system that includes at leastone receiver (1802) and one transmitter (1800) connected via a wirelessdata link (1804); the transmitter (1800) and receiver (1802) areseparated, in FIG. 18, by a receiver-measured distance (1808). A button(1812) pressed on the transmitter (1800) by the operator (1810) commandsthe transmitter to send data representing the measured field strength atthe transmitter (as measured by current in the coil or by an integratedfield strength sensor (1806). The transmitter (1800) also sends any datarepresenting known failure conditions discovered at test duringinitialization of the transmitter. The receiver compares the receivedfield strength measurement with its own detection of field strength,taking into account the measured (1808) distance between the twodevices, as a diagnostic assessment.

FIG. 19 illustrates a portable locating system comprising a transmitter(1900) which is connected by a “smart” inductive clamp (1904) to autility conductor, and is connected via wireless data link (1906) to areceiver/locator (1902). The receiver is equipped with a data storagedevice such as a removable card or memory unit (1914). In FIG. 19, thetransmitter (1900) has detected a new device added to the network in theform of the clamp (1904). The clamp device sends its own identification(1908) to the transmitter. The transmitter, in response to the detectionof a new device, transmits to the receiver/locator a data set (1912)including its own identification, model and serial number, availablefrequency and power values, its software version, manufacture data, anysensor data available, its current mode setting, the clamp ID and type,the kind of utility to which it is connected, and its own battery level,as examples. It thus becomes possible for any device in the mesh networkto know what other devices are in the network.

FIG. 20 illustrates a portable locating system comprising a transmitter(2000) connected to a utility line (2010) by means of an inductive clamp(2004), and connected via wireless data link (2006) to areceiver/locator (2002). In FIG. 20, the transmitter has encountered alow-battery condition and is sending a status message (2012) to theother elements in the network (in this case, the receiver/locator)informing them that the transmitter will shut down in ten seconds. Otherstatus conditions could equally be transmitted among system elements asappropriate for each element.

FIG. 21 illustrates a portable locating system comprising a transmitter(2100) connected to a utility line (2110) by means of an inductive clamp(2104), and connected via wireless data link (2106) to areceiver/locator (2102). In FIG. 21, The transmitter (2100) is alsocapable via an integrated GPS receiver of receiving GPS time-taginformation from a GPS satellite (2114). The transmitter, on receipt ofGPS time information, executes a “set clock” routine and also transmitsa time stamp message (2112) over the data link (2106). On receipt of thesynchronizing message, the receiver/locator (2102) likewise performs a“set clock” routine. In similar wise, any element which is incommunication with an external clock, such as a GPS time signal, canserve to synchronize time throughout the system group.

FIG. 22 illustrates a portable locating system comprising a transmitter(2200) which communicates to a receiver locator (2202) via wireless link(2212) and to a second receiver/locator (2204) via a second wirelesslink (2210). The second receiver/locator (2204) also links wirelessly(2208) directly to the first locator/receiver (2202). A GPS satellite(2206) transmits location information which can be received by any ofthe three devices via wireless links (2214 a, 2214 b, 2214 c). Locationinformation can thus be received by any device and exchanged with anyother device in the group, providing increased positional accuracy. Inaddition to GPS location, any node in the wireless network may alsoinclude an inertial navigation module enabling it to track and reportlocation independent of, or as a verification of, GPS locational data.

FIG. 23 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which the receiver (2302) commands a transmitter (2300) toonly source the amount of current needed for a strong and stable signalthereby conserving available battery energy. The transmitter (2300) islinked to the locator/receiver (2302) by wireless link (2306) on whichit sends the current values, and on which it receives the instructionmessage (2312). The transmitter then adjusts output current injectedonto the target utility (2310) via an inductive clamp (2304). Thelocator/receiver (2302) can be set to automatically adjust its soundgain level such that the sound does not change with variations in outputcurrent. Thus, the system group can maintain a target signal level atthe receiver/locator (2302) in a series of adjustments that aretransparent to the operator.

FIG. 24 illustrates a portable locating system comprising alocator/receiver (2402) with a wireless link (2406) to a transmitter(2400) which is connected via an inductive clamp (2404) to a utilityconductor (2410). In FIG. 24, a phase timing signal (2408) is sent fromthe transmitter (2400) to the locator/receiver (2402); optionally, acorresponding phase timing signal (2412) could be send from thetransmitter (2400) by injecting it onto the utility conductor (2410).Based on this signal, relative phase of the transmitted signal can bedetermined at the locator/receiver (2400) and use in improving theprecision of the locate results.

FIG. 25 illustrates a portable locating system comprising alocator/receiver (2500) used in conjunction with a pipe inspectioncamera system (2502) which includes an integrated sonde (2506) which isbuilt in to the camera head (2504), moved through the pipe by means of apush-cable (2514). See pending U.S. Patent Application Ser. No.60/864,104, filed Nov. 2, 2006, entitled “Pipe Mapping System” of MarkS. Olsson et al., the entire disclosure of which is hereby incorporatedby reference. The sonde emits a dipole field. In addition to the sonde'sfield, a tracing frequency (e.g., 32768 Hz) can be injected into thecable connected to the camera, which can then be used by thelocator/receiver (2500) to detect the path of the camera head. Awireless link (2512) connects the locator/receiver (2500) with the pipeinspection control unit (2502) and data items are exchanged between thetwo units. The locator/receiver (2500) sends detected sonde depth,detected signal strength at each antenna, commands to turn thetransmitter on or off, and “over sonde” messages to the pipe inspectioncontrol unit (2502). The pipe inspection control unit (2502) may sendpushcable count, sonde power status, camera tilt angle and sonde angleinformation to the locator/receiver (2500). In addition to the directvideo from the camera head (2504) key information (e.g., depth of pipe)can be displayed on the user interface (2510) display; if thelocator/receiver (2500) is equipped with an integrated compass unit, theorientation of the pipe relative to true or magnetic North can also bedisplayed and recorded on the video. The route of the locator/receiver(2500) along the trace signal (2508) can be captured and mapped.

FIG. 26 illustrates a portable locating system in which amulti-frequency capable inductive transmitter (2600) and areceiver/locator (2602) are connected by a wireless link (2604). Seepending U.S. Patent Application Ser. No. 60/871,268, filed Dec. 21,2006, entitled “High-Q Self Tuning Location Transmitter” of RayMerewether et al., the entire disclosure of which is hereby incorporatedby reference. In FIG. 26 the receiver/locator (2602) sends a commandsignal to the transmitter (2600) to transmit on frequency 1 (f1), andthen on frequency 2 (f2), Transmitter (2600), on a routine schedule,optionally publishes signal strength data and current level data. InFIG. 26, a display message can be shown on the locator/receiver (2602)instructing the operator not to move the instrument while the orderedfrequencies are being applied. By comparing the change of the receivedsignals as a function of frequency, the locator/receiver (2602) can thencalculate the degree of air-coupling, based on the difference betweenthe rate of signal degradation through air (1/R³) compared to the rateof signal degradation on a conductor (˜1/R). By compensating for aircoupling, it becomes possible for the locator/receiver (2602) to locatehidden utilities closer to an inductive dipole source. Magnetic fieldstrengths can be measured at the transmitter and communicated to nlocator/receivers in the system group.

FIG. 27 illustrates an aspect of the invention in which a portablelocating system includes at least one receiver (2702) and onetransmitter (2700), that can each communicate by wireless means (2706),in which a rotating or tilting means (2704) is integrated into, orcombined with, an inducing transmitter (2700). In FIG. 27, a “rotate”command may be sent from the receiver/locator (2702) to the rotatingelement (2704) which causes the inductive transmitter (2700) to changeits angle relative to a target line (2710 a). In application, thisability would be used to bring about a null response from the targetline (2710 a) by adjusting the angle of the emitted field to theconductor, allowing an adjacent nearby utility line (2710 b) to beseparately identified and located.

FIG. 28 illustrates a portable locating system that includes at leastone receiver and one transmitter that can each communicate by wirelessmeans, in which the system group network is extended to include avariety of other devices used in location and detection tasks. In FIG.28, network relay is accomplished via a WAN Link (2822) from a celltower (2820), a separate data relay node device (2802), a GPS satellite(2828) and an Iridium satellite (2824). The devices which are networkedin the group include a geophone (2804), an A-frame fault detector(2808), and a sonde (2810) of the type used in Horizontal DirectionalDrilling (HDD) applications; the sonde is physically connected to adrill string operated from a HDD machine with an integrated controllerand display (2806). The HDD drill string is optionally energized by aseparate transmitter (2828). An optional power and data link (2826) wireline may be incorporated with the HDD drill string. A distantreceiver/locator (2818) with integrated GPS and mapping capabilities isused to track the HDD Sonde. The receiver/locator is connected bywireless links (2812, 2816, 2818) to the data relay node (2802), theacoustic geophone (2804) and the A-frame fault locator (2808),respectively. The data relay node (2802) also maintains a wireless link(2814) with the HDD machine (2806). Each linked device in the extendedgroup may publish its status and other key data, and any device in theextended group may subscribe to appropriate information published byother devices. An Inertial Navigation module (INS) may be included inany unit as a means of tracking its location independent of GPS signals.

FIG. 29 illustrates a portable locating system that includes at leastone receiver (2902) and one transmitter (2900) that can each communicateby wireless means in which an operator (2916) publishes via wirelessdata link (2908) from a transmitter (2900) data describing the type ofconnection point to which the connection is made (e.g., tracer wire,transformer, valve, meter). In FIG. 29, the transmitter is connected toa buried utility (2912) via a tracer wire leading to the gas meter(2906) such as is typically installed on non-conductive piping for thispurpose. The operator can communicate the type of connection point viathe user interface of the transmitter (2900) or the user interface ofthe locator/receiver (2902) where the data can optionally be stored tomemory card or other data storage device (2918). The communication fromthe operator to the user interface of either device can be made by anyknown means including but not limited to keypad, touch screen or voiceinput.

FIG. 30 illustrates an extended portable locating system of devicesincluding a dipole signal beacon (3006), a second dipole signal beaconequipped to receive GPS signals (3004), a receiver/locator withintegrated mapping capabilities (3000), a third dipole beacon integratedwith a laser range finder (3002), and a remote computer (3008). Becauseof the wireless links networking the mapping-enabled locator/receiver(3000) with multiple dipole beacons, GPS information and ranges producedby a laser range-finder (3002), the system group can produce integratedmapping information which is them relayed to the remote computer (3008)for post processing, integration into a larger data set, supervisoryoversight, training purposes, or other uses. In FIG. 30, a laserrange-finder (3002) has an integrated 3-axis compass and an integrated3-axis tilt sensor to allow the position of point A (3010) to bedetermined

FIG. 31 illustrates a portable locating system comprising alocator/receiver (3102) connected by a ZigBee wireless link to atransmitter (3100). In FIG. 31, the locator/receiver's ZigBee linkreceived signal strength is used as the basis of estimation of theproximity to the transmitter (3100), and the transmitter is operating aroutine by which it will emit a “ping” sound when the communicatedsignal strength exceeds a set value x. Similarly, in this aspect, thelocator/receiver will display a particular icon representing thetransmitter when the communicated signal strength exceeds some value y,thus allowing the operator to be aware of his relative proximity to aparticular transmitter, or to be guided toward it by the transmitter's“ping” sounds.

FIG. 32 illustrates a portable locating system comprising alocator/receiver (3202) linked by wireless data link (3204) to a distanttransmitter (3200) which is connected to a utility (3210). In FIG. 32,the transmitter in response to instructions from the locator/receiver istime-multiplexing two (or more) frequencies, here marked f1 and f2. Thetiming signals (3206) are sent wireless while the frequencies aretransmitted on the utility conductor (3210). By using narrow band shorttime constant (or FIR) filters in front of a correlation based receivingchannel, the output of the transmitter is rapidly switched between twodifferent output modes, and the receiver remains relatively insensitiveto phase shifts. If the apparent position of a utility changesappreciably at different frequencies, as shown on the locator/receiverdisplay, then other coupled utilities are indicated. If the depth movedvertically, (f1 depth is different from f2 depth) between the differentfrequencies, then a depth correction may be required.

FIG. 33 illustrates a portable locating system comprising a transmitter(3300) which is directly connected to a utility (3310) and connected bywireless link (3304) to a locator/receiver (3302). In FIG. 33, thelocator/receiver (3302) performs sampling of the ambient electromagneticfrequency domain, using FFT or other methods, in order to identifyfrequencies which will produce improved signal to noise ratio in thelocating process; the calculated optimum frequency is then set on thetransmitter by means of a wireless control link (3304) betweenlocator/receiver (3302) and transmitter (3300).

FIG. 34 illustrates a portable locating system in which a transmitter(3400), while not actively transmitting, monitors the amplitudes ofvarious signal peaks and harmonics and transmits across a wireless link(3406) computed FFT “frequency bins” to the locator/receiver (3402). Thelocator/receiver in turn compares and tunes its digital filters againstthe profile of the transmitter-provided FFT data to optimize thesignal-to-noise ratio in the locating process. The use of the monitoredinformation as a “fingerprint” of the connected utility can then enablea second receiver to confirm that it has detected the same utility or adifferent one. Analog-Digital Converter (ADC) information can besimilarly transmitted instead of FFT frequency bin data; transmissioncan be via ZigBee, Bluetooth or other means.

FIG. 35 illustrates a locating system group comprising a primarylocator/receiver (3500) from which screen display data is transmittedwirelessly to a projection device (3504) and simultaneously transmittedto a “slaved” student locator/receiver as a training method.

FIG. 36 illustrates a locator/receiver (3600) connected via cell towerto a remote computer (3602). In FIG. 36, locating events displayed onthe locator/receiver are displayed as well on the remote computer (3602)for purposes such as training or supervision, and optionally may bestored and archived on the remote computer or some network to which itis connected.

FIG. 37 illustrates a portable locating system comprising alocator/receiver (3700) connected via wireless data link (3706) to adistant transmitter (3702) being managed by an operator (3704). In FIG.37, the operator transmits an instruction to the locator (3700) via akeypad on the transmitter instructing the locator/receiver (3700) tosend data describing the received signal strength at the locator back tothe transmitter (3702). Based on the resultant audio output from thetransmitter's speaker, or from data on an LCD display, the operator maymove the transmitter (for example, to either side of the line) in orderto find a maximum signal or a null signal. This aspect provides anothermeans for an operator to enhance the accuracy of a locate procedure.

FIG. 38 illustrates a portable locating system comprising alocator/receiver (3800) linked by wireless connection to a proximatedata-relay node device, or repeater. The node device is linkedwirelessly to a second node device (3806) which is in turn linkedwirelessly to a distant transmitter (3802). In FIG. 38, the node devicesserve to extend the mesh network between the other devices, and enablethe network to extend around an obstacle such as a building (3804) orsimply increase the mesh network's range.

FIG. 39 illustrates the use of a frequency shifting re-transmitter. Sucha frequency shifting re-transmitter is preferably wireless enabled butthis is not a requirement. By way of example a cable fault findingA-Frame application is shown. In this example frequency shifting allowsthe receiver to separate signals (3934) radiated directly from line(3908) from those transmitted by antenna (3916). Transmitter (3912)transmits a coded signal by way of direct connection (3928) to utility(3908). Receiver (3900) can use this signal to locate the hiddenutility. Fault (3910) causes voltage potentials in the ground inassociation with the localized fault. This time varying potential iscauses a voltage between electrodes (3904, 3906). Frequency shifter(3922) mounted on A-Frame supporting structure (3902) amplifies asneeded these voltages and then frequencies shifts this time varyingsignal by some predetermined amount using known means such as hardwareanalog or software digital mixers and then retransmits thisfrequency-shifted signal on antenna (3916). The electrical connectionbetween electrodes (3904, 3906) is provided to frequency shifter (3922)by means of docking electrical connections (3918, 3920) respectively.Receiver (3900) can display on its user interface a corresponding signalstrength value for the electrical potential measured between electrodes(3904, 3906). The A-frame can be moved from location to location and thesignal variations can be used by known means to localize the faultlocation. Optionally the measured signal strength determined by receiver(3900) can be sent by wireless means to frequency shifter (3922) whichcan optionally display this information on a user interface (3936). Thiscapability helpfully allows an operator to easily see which electrode isclosest to the fault. Optionally compasses (not shown) in the receiverand in the re-transmitter provide information to allow the groundcontact electrode orientation relative to that of the receiver to bedetermined.

FIG. 40 illustrates a plan view of one embodiment of a three channelspatial re-transmitter (4002) used in conjunction with three geophones(4004, 4006, 4008) and a tripod, four antenna node (12 channels)receiver. Each geophone may optionally include a dipole Sonde (notshown) to allow positional determination by receiver (4000). In oneembodiment, each Sonde transmits a separate frequency. In anotherembodiment, a transmission sequence is employed and wireless link 4016is used to communicate the time sequence to receiver (4000). The signalreceived by each geophone is amplified and transmitted on separate wirecoil antennas (4014 a, 4014 b, 4014 c). A high pass filter might beemployed on each channel before transmission. Geophones in this mannercan be used to isolate and determine the location of a leak in a pipingsystem. In conjunction with external sound sources, either fixed ormovable, either with or without beacon Sondes, acoustic tomographytechniques can be employed for imaging purposes. We have demonstratedthat the antenna structure (4018) used in the receiver, can also be usedas an antenna (4012) to transmit signals at frequencies suitable for usewith geophones.

FIG. 41 illustrates two portable locating systems may be connected andtheir network operation extended through the introduction of anintermediary longer-range communication link. In FIG. 41, alocator/receiver (4100), operating as part of a mesh network (not shown)is linked by wireless (e.g., ZigBee or similar) communication link(4108) to a long-range RF relay device (4110). Device (4110) is linkedby long-range wireless communication link (4104) to a similar relaydevice (4112) serving a distant mesh network locating system groupcomprising a transmitter (4102), in this example. Any data exchangedbetween the various devices described in the above figures may thus belikewise transmitted and received among more distant mesh-networkedgroups. Additionally, it will be appreciated that the long-distance linkmay be any wireless or physical connection (for example, RF, microwave,fiber-optic, or wired connection) as appropriate to the individualapplication.

FIG. 42 illustrates a detailed view of a particular device which may beemployed in a locating network, known as a Locating Ranging beacon. InFIG. 42, a marker, as an example, similar in form to a common trafficcone, is equipped with devices with which to participate in a locatinggroup. In FIG. 42, a ranging beacon 4200 is equipped with a battery pack4202 which powers an LED power signal 4208, a time-of-flight rangingtransceiver 4216, an optional GPS receiver 4214, optional GPS compass4212, and the connections between these components. An optional magneticcompass 4210 may also be installed which may be equipped with digitaldata output. The beacon includes an antenna 4201 capable of receivingGPS signals, or signals from comparable systems such as Galileo,GLOSNASS, etc. An optional radio antenna 4206 is also shown capable oflinking the cone to a wireless data network and/or wireless rangingsystem. The ranging cone device 4200 can be used to define the limits,for example, of a locating area within which a locator, transmitter andother components of a locating group are operating. In addition to orinstead of GPS satellite locational information, a “pseudolite,” orsynthetic GPS signal may be used to provide a reference datum, Astandard GPS pseudolite is a single channel (L1) GPS pseudolite designedfor a standalone signal source. Alternatively a synchronizedpseudolite—a pseudolite set containing synchronization SW and referenceGPS receiver—may be used. This provides means to synchronize thepseudolite clock to external GPS time. The use of a cone is as exampleas only. The devices shown could alternatively be packaged in some otherform for convenience in use. The MAXIMUM power that a pseudolite isallowed to transmit is 1 microwatt. If the cone or beacon also containsa GPS receiver, the GPS receiver can be used to generate the ephemerisinformation for the pseudolite to transmit. The utility locator containsa GPS receiver which is used to provide positional information of thelocator relative to the pseudolites. This is another type oftime-of-flight positioning system.

FIG. 43 illustrates one possible configuration in which ranging beaconscan be deployed. In FIG. 43, four beacons configured as cones (4302,4304, 4306 and 4308) are deployed to define a locating area within whicha locator receiver 4310 equipped with a ranging transceiver 4312, alocating transmitter 4316, similarly equipped with a rangingtransceiver, and a stationary dipole beacon 4314 (preferably alsoequipped with a ranging transceiver), are deployed. Dipole beacon 4314is optional. A buried conductor such as a pipe or cable 4318 is shown.Within such a deployment, the mesh network of the locating groupexchanges near real-time positional information, with the four cones4302-4308 providing a baseline measurement against which mobilepositions may be calibrated. Positional information is supplemented bythe locator receiver 4310 sensing the location of the dipole beacon 4314independently. It is advantageous if both locator 4310 and the dipolebeacon 4314 are equipped with compasses allowing the relativeorientation of both the dipole with a horizontal axis and the locatorare known. Alternately, the dipole beacon 4314 can be oriented to aknown compass orientation using a magnetic compass mounted on top.Additional advantages are offered if the dipole beacon 4314 isphase-coded providing an indication of which pole of the beacon isnorth-pointing, due to the additional certainty provided by the knowndipole field orientation. In FIG. 43, each unit equipped with a rangingtransceiver has a wireless link 4322 with each other such unit. Locator4310 includes the capability to detect and measure the dipole field 4320from dipole beacon 4314.

FIG. 44 illustrates the use of “time-of-flight” ranging between devices.In FIG. 44, four ranging cones 4302, 4304, 4306, 4308 define a locatingarea, with each cone containing a wireless time-of-flight rangingtransceiver. Other devices are available on the market which would serveequally well, utilizing the IEEE 802.15.4a wireless standard or asimilar specification. Range determination could also be achieved usingRSSI in addition to or instead of time-of-flight measuring. In FIG. 44,each transceiver is capable of sending and receiving identifiable radiopulses which include unit ID and time tags. At least one of the units iscapable of computationally deriving the distance between each pair ofunits based on the time of signal travel from one of the othertransceivers. Using this information, a real-time log of distances and agraphic display of relative locations between units can be displayed,archived, transmitted, or relayed to a base computer for integrationinto some other information system such as GIS. A tripod locatorreceiver 4402 is equipped with its own time-of-flight rangingtransceiver 4404. In addition, an Inertial Navigation System (INS)module 4406 can be optionally affixed to the locator receiver and usedto provide finer-scale measurement of the locator's movement resultingin more precise representation of its location within the operatingarea.

FIG. 45 illustrates the operation of a five-node “time-of-flight”network is illustrated in an aerial view. Four transceivers 4504, 4506,4508, and 4510 define the outer limits of the area of operation. Eachtransceiver includes an integrated circuit for receiving, timing andtransmitting signals. A fifth unit 4502, known as the Tag unit, ismobile within the range of the corner units 4504, 4506, 4508, 4510. Inoperation, each unit transmits data signals using an establishedprotocol such as IEEE 802.15.4a. See U.S. Pat. No. 6,404,338 B1 ofKoslar granted Jun. 11, 2002, the entire disclosure of which isincorporated by reference. The transceivers typically operate in the2.45 GHz frequency range using frequency-division multiple access (FDMA)channels. Thus, one channel might have a center frequency of 2412 MHz,another 2437 MHz, and a third channel 2462 MHz.

In FIG. 45, the Tag unit is here linked to a laptop computer display4512, although any computational device could be used, such that themoment by moment stream of computed distances from the Tag unit 4502 toeach other unit is received. The ranging information may be displayed asa text stream or integrated into a geographical display, for example, orotherwise processed as required to support mesh-network operations.

It should be noted that while the exemplary system shown usestime-of-flight calculation for determining distance measurements amongtransceivers, the system could alternately employ Received SignalStrength Indication (RSSI) analysis to improve mapping accuracy eitheralone or in combination with time-of-flight measurements.

Turning now to FIG. 46, a further method of refining positionalinformation in a locating group which may be associated with a meshnetwork is shown. In FIG. 46, a tripod locator 4602 is shown in whichground-tracking sensor transducers 4604, 4606, 4608 have been affixed tothe three legs of the locator receiver. In this example configuration,the three transducers can send a sonic pulse and detect and time thereturn signal from the ground while the locator is in motion over theground. The Doppler variation in the sonic signals provides the basisfor computing the movement and rate of movement of locator 4602 relativeto the ground. This data is provided as needed to other units in thelocating group. The Doppler information can be used separately from orin combination with any other navigational or mapping information suchas provided by inertial navigation modules or radio-based navigationsystems. Radar on laser Doppler technique can also be used.

Turning now to FIG. 47, an alternative embodiment is illustrated forrefining locational information using Doppler calculations andground-tracking sonar transducers. In FIG. 46, a single-legged locator4702 is equipped with downward angled sonar transducers 4704, 4706 onthe inner edges of the gradient coil antenna housings 4708, 4710. Thetransducers, like those in FIG. 46, send sonar pulses and receivereturns from them while the locator is in motion producing differentialDoppler effect data from which motion data can be derived.

Turning now to FIG. 48, an alternative embodiment is illustrated whichemploys sonar to refine positional information. In FIG. 48, a single-leglocator 4802 is equipped with a correlation sonar array 4804 affixedbelow the lower antenna node. This array typically comprises onetransmit unit and, for example, nine receiving sensors in a single 600kHz array. A correlation sonar array provides fine measurement ofdisplacements with less drift than the Doppler method in FIGS. 46 and47. It should be noted that Doppler computations are not limited tosonar frequencies; laser, radar, or sonar could be used, for example toprovide Doppler information for locational precision.

Turning now to FIG. 49, an embodiment of the present invention includesa portable display and communication device 4904 which is affixed to alocator receiver 4902 in a formed receptacle for that purpose andconnected by means of a cable interface 4906 or similar means. Thedisplay and communication device acts as information display andcommunication unit for data or voice. The display and communicationdevice may be adapted from commercially available units such as theiPhone from Apple, Inc., or it may be custom manufactured according toapplication requirements.

Turning to FIG. 50, an embodiment of the present invention includes aportable display and communication device 5004 affixed to a pipeinspection system 5002. In FIG. 50, the portable display andcommunication device 5004 may be connected by a built-in plug (notshown), for example; the portable display and communication deviceserves to display information relating to the processes of the pipeinspection system, and may serve to provide network connection and dataor voice communication.

Clearly, other embodiments and modifications of this invention may occurreadily to those of ordinary skill in the art in view of theseteachings. For example, our invention need not employ a meshed network.Each and every radio link herein disclosed in all of the variousembodiments can be usefully configured for time of flight ranging toprovide a distance between two transceivers. Additional transceivers canalways be provided if position information is needed. The presentinvention broadly includes the concept of using time of flight ranginginformation to provide relative positioning of a man portable pipe andcable locating device. Therefore, this invention is to be limited onlyby the following claims, which include all such embodiments andmodifications when viewed in conjunction with the above specificationand accompanying drawing.

1. A system for locating a hidden utility, comprising: a man portablereceiver/locator; and wireless communication means for establishing ameshed network with a plurality of nodes including the receiver/locatorand at least one transmitter configured to inductively or directly applya signal to the hidden utility; wherein the transmitter is configured tochange a characteristic associated with the applied signal in responseto a command received from a node of the mesh network.
 2. The system ofclaim 1 wherein the nodes of the meshed network includes one or morenodes selected from the group consisting of an A-frame fault detectiondevice, a conductor-identifying stethoscope, a ground penetrating radardevice, and a remote geophone.
 3. The system of claim 1 wherein thereceiver/locator is configured to determine an amount of cross couplingassociated with adjacent utilities based on a measurement of one or morefield angles.
 4. The system of claim 1 wherein the wirelesscommunication means is configured to broadcast information to othernodes of the network at predetermined intervals.
 5. The system of claim1 wherein the man portable receiver/locator includes means for causingthe transmitter to apply a plurality of signals at different frequenciesand determining an optimum frequency for determining a location of thehidden utility.
 6. The system of claim 1 wherein the man portablereceiver/locator includes a plurality of ground tracking transducers andmeans for deriving positional information based on Doppler shiftsdetected by the transducers.
 7. The system of claim 1 wherein thereceiver locator includes means for determining a location of the hiddenutility based on time-of-flight positioning between thereceiver/locator, the one transmitter and at least one ranging beacon.8. A system for locating a hidden utility, comprising: a man portablereceiver/locator; and wireless communication means for establishing ameshed network with a plurality of nodes including the receiver/locatorand at least one transmitter configured to inductively or directly applya signal to the hidden utility; wherein the man portablereceiver/locator includes means for calculating a predetermined signalquality metric and commanding the one transmitter to increase ordecrease transmitted current in order to meet the predetermined signalquality metric.
 9. A method of locating a hidden utility, comprising thesteps of: providing a man portable receiver/locator; providing at leastone transmitter configured to inductively or directly apply a signal toa hidden utility; and wirelessly communicating between the man portablereceiver/locator and the transmitter to apply a signal to the hiddenutility in a predetermined manner that optimizes the locating process,and wherein the communication is performed by treating the portablereceiver/locator and the one transmitter as nodes of a meshed network.10. The method of claim 9 wherein the meshed network includes pipeinspection camera configured to receive data indicating Sonde signalstrength from the receiver/locator.
 11. The method of claim 9 whereinthe communication is performed according to a ZigBee protocol.
 12. Themethod of claim 9 wherein the man portable receiver/locator causes theone transmitter to apply a plurality of signals at different frequenciesand then determines an optimum frequency for determining a location ofthe hidden utility.
 13. The method of claim 9 and further comprising thestep of broadcasting information to the other nodes of the network atpredetermined intervals.
 14. The method of claim 9 wherein the manportable receiver/locator derives positional information based onDoppler shifts detected by a plurality of ground tracking transducers.15. The method of claim 9 wherein the meshed network contains three ormore nodes selected from the group consisting of a receiver/locator, anA-frame fault detection device, a conductor-identifying stethoscope, aground penetrating radar device, a remote geophone, a GPS receiver, anda transmitter configured to inductively or directly applying a signal toa hidden utility.
 16. The method of claim 9 wherein the man portablereceiver/locator communicates with a plurality of ranging beaconsdeployed to define a locating area.
 17. A method of locating a hiddenutility, comprising the steps of: providing a man portablereceiver/locator; providing at least one transmitter configured toinductively or directly apply a signal to a hidden utility; andwirelessly communicating between the man portable receiver/locator andthe transmitter to apply a signal to the hidden utility in apredetermined manner that optimizes the locating process, and whereinthe communication is performed by treating the portable receiver/locatorand the one transmitter as nodes of a meshed network; wherein the manportable receiver/locator calculates a predetermined signal qualitymetric and commands the one transmitter to increase or decreasetransmitted current in order to meet the predetermined signal qualitymetric.
 18. A method of locating a hidden utility, comprising the stepsof: providing a man portable receiver/locator; providing at least one;wirelessly communicating between the man portable receiver/locator andthe transmitter; causing the transmitter to apply a signal to the hiddenutility in a predetermined manner that optimizes the locating process;and determining a location of the hidden utility based on time-of-flightpositioning between the receiver/locator, the one transmitter and atleast one ranging beacon.